1. Field of the Invention
The present invention relates in general to seat slide devices of a motor vehicle, and more particularly to seat slide devices having lock mechanisms incorporated therewith. More specifically, the present invention is concerned with seat slide devices of a type which comprises two parallel slider units each including a lower rail secured to a floor and an upper rail slidably disposed on the lower rail and a seat mounted thereon, two lock mechanisms respectively associated with the two slider units for locking the upper rails at desired fore-and-aft positions relative to the lower rails, and a lock releaser incorporated with both the two lock mechanisms for cancelling the locked condition of the lock mechanisms when manipulated.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional seat slide device having a lock releaser 6 will be described with reference to FIG. 5 of the accompanying drawings.
The seat slide device comprises two slider units 1 and 1' (viz., right and left slider units) which are arranged in parallel with each other. Each unit comprises a lower rail 3 connected to a floor (for example, a vehicle floor) and an upper rail 4 slidably disposed on the lower rail 3 and a seat (not shown) mounted thereon.
The lock mechanisms are respectively associated with the two slider units. Each lock mechanism comprises a plurality of notches 5 formed in the lower rail 3, a locking lever 9 pivotally supported by a support lug 4a of the upper rail 4, a pawl (not shown) carried by the locking lever 9 and latchingly engageable with the notches 5, and a biasing spring 2 for biasing the locking lever 9 in a direction to achieve the latching engagement between the pawl and a selected one of the notches 5.
The lock releaser 6 is of a generally U-shaped bar which has leg portions 8 and 8 respectively secured to the pivotally supported locking levers 9 of the two slider units 1 and 1'. Denoted by numeral 7 is a handle portion of the bar 6, which is to be manipulated by an operator (viz., a seat occupant) when position change of the seat position is required by him or her.
Due to the force of the biasing springs 2, the pawl of the locking lever 9 of each slider unit 1 or 1 is kept engaged with one of the notches 5 of the lower rail 3 locking the upper rail 4 at a desired fore-and-aft position relative to the lower rail 3.
When, for the purpose of changing the seat position, the handle portion 7 of the bar 6 is raised by an operator (viz., a seat occupant) against the force generated by the biasing springs 2, the pawl of the locking lever 9 of each lock mechanism is disengaged from the notch 5 cancelling the locked condition of the upper rail 4. Thus, under this condition, the seat is permitted to move forward or rearward to a new desired position.
When the seat is moved to the new position, the handle portion 7 of the bar 6 is released from the operator's hand. With this, the pawl of the locking lever 9 of each lock mechanism is brought into engagement with a newly selected one of the notches 5 by the force of the biasing spring 2. Thus, the seat becomes locked at the new position.
However, the above-mentioned seat slide device has the following drawback particularly when the same is of a type wherein an end of a seat belt B is connected to one of the upper rails 4, for example, the upper rail 4 of the left slider unit 1' as shown in FIG. 5.
That is, when, due to a vehicle collision or the like, the seat belt B is applied with an excessive load by a belt wearer on the seat, the upper rail 4 to which the seat belt B is connected tends to be raised or deformed separating from the lower rail 3 as is shown by a phantom line. The raising of the upper rail 4 may cancel the locked condition of the lock mechanism mounted to the left slider unit 1'. In addition to this undesired phenomenon, the raising of the upper rail 4 causes an upward movement of the handle portion 7 of the bar 6, and thus, similar to the case of the lock releasing operation properly effected by the operator, the locked condition of the other lock mechanism mounted to the right slider unit 1 tends to be cancelled. These phenomena may induce a dangerous slippage of the seat on the lower rails 3 upon such vehicle collision.